engine cleanup passes 4-7 + multi-instancing ambient rip

Squashes 146 commits from battle-engine-extraction. Net: 2,045 files changed,
+11,896 / -158,687 lines. Ships engine passes 4-7 (dead-code cull, view-layer
stub, receive-path shrink) plus the Phase-5 AsyncLocal ambient deletion that
turns concurrent battles into a type-system property rather than a scope
contract.

## What landed

**Passes 4-7 (chunks 1-34):** Extended the Phase-4 const-false collapse into a
cascading cull across the skill graph, view layer, and receive-path periphery.
Six mode flags (IsWatchBattle/IsReplayBattle/IsAdmin/IsAdminWatch/IsPuzzleQuest/
IsAINetwork) became `const false`, every guarded block deleted. Field*.cs
subclass ctors + BackGroundBase + ObjectChecker culled to no-ops. Mulligan
family reworked to take a mgr param through IMulliganMgr.InitMulligan.
Emotion/Recovery/Resource clusters null-stubbed. Prediction/OperationSimulator/
skill filters converted from static ambient reads to per-mgr reads via
SkillPrm.ownerCard.SelfBattlePlayer.BattleMgr / ins.BattleMgr / this.BattleMgr.

**Phase-5 ambient rip (chunks 35-47):** Deleted BattleAmbient / BattleAmbient-
Context / TestBattleScope in full. Every per-battle mutable slot now lives on
the mgr instance itself:
  mgr.InstanceIsForecast / InstanceIsRandomDraw / InstanceRecoveryInfo /
  InstanceViewerId / InstanceNetworkAgent / GameMgr
BattleManagerBase.GetIns() returns null unconditionally; the residual static
flags + 3 façades (Certification.ViewerId, Data.BattleRecoveryInfo,
ToolboxGame.RealTimeNetworkAgent) are null-tolerant defaults kept for the
handful of engine-internal readers that still reference their types. Zero
BattleAmbient references anywhere in engine + node + tests.

Added pre-seeded GameMgr ctor overload threaded through the mgr chain
(BattleManagerBase → SingleBattleMgr / NetworkBattleManagerBase → NetworkStandard-
BattleMgr → HeadlessBattleMgr / HeadlessNetworkBattleMgr). Fixtures build a
GameMgr, seed it via HeadlessEngineEnv.SeedCharaIds/SeedNetUser, and pass it
to the mgr's ctor — no ambient reach.

Node side (SVSim.BattleNode/SessionBattleEngine): _ctx replaced with a plain
GameMgr field; 34 `using var _ambient = BattleAmbient.Enter(_ctx)` scope wraps
ripped from every accessor and mutator; EngineGlobalInit.WirePerSessionGameMgr
takes GameMgr as a param and runs from SessionBattleEngine.SetupInternal
BEFORE mgr construction.

Test side: TestBattleScope deleted; 18 fixture [SetUp]s migrated to
`HeadlessEngineEnv.EnsureProcessGlobals()`; MultiInstanceEngineTests rewritten
around per-mgr construction (GetIns() → null is the pinned invariant).

## Regression fixes

- **chunk-48** (MulliganCtrl): chunk-35's `= null` stubs on card lookups broke
  the live receive-driven Deal path (BattlePlayerBase.DrawCard NRE'd downstream
  of NetworkPlayerMulliganCtrl.StartMulliganVfx). Restored the three lookups
  via `_battlePlayer.BattleMgr.GetBattleCardIdx`. Engine tests were satisfied
  by the WireMulliganPhase seam; unit tests exposed the live-path gap.

## Ship state

- SVSim.BattleEngine.Tests: 56/56 pass, 2 skip
- SVSim.UnitTests: 1554/1554 pass (was 1523/31-fail before chunk 48)
- Solution build: 0 source warnings (40 pre-existing NU1902 MessagePack CVEs
  in SVSim.EmulatedEntrypoint, unrelated)
- Sequential PVP smoke: verified live (two back-to-back battles, no regression
  on cleanup/spinup)
- Concurrent PVP smoke: verified live

Adds tools/engine-port/ClosureAnalyzer/ — the Roslyn transitive-type-closure
analyzer needed to make future cascade cleanup safe (per feedback memory
"Engine cleanup needs closure tool" from the 2026-06-28 pass-3 failure).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

SVSim.BattleEngine/Rng/HeadlessBattleMgr.cs

@@ -23,6 +23,14 @@ namespace SVSim.BattleEngine.Rng
             _rng = rng ?? new SeededRandomSource(contentsCreator.RandomSeed);
         }
 
+        // Phase-5 chunk 45: overload for the pre-seeded GameMgr path — fixtures build a GameMgr,
+        // seed it (SeedCharaIds + SeedNetUser), then hand it to this ctor. Retires the ambient bridge.
+        public HeadlessBattleMgr(IBattleMgrContentsCreator contentsCreator, IRandomSource rng, GameMgr gameMgr)
+            : base(contentsCreator, gameMgr)
+        {
+            _rng = rng ?? new SeededRandomSource(contentsCreator.RandomSeed);
+        }
+
         // KNOWN DIVERGENCE: the base StableRandom/StableRandomDouble also bump a private
         // `stableRandomCount` diagnostic field; these overrides cannot (it's private to the base) and do
         // not. The field is currently unread anywhere in the engine, so this is harmless; if a future

SVSim.BattleEngine/Rng/HeadlessNetworkBattleMgr.cs

@@ -1,3 +1,7 @@
+// TODO(engine-cleanup-pass2): 1 of 3 methods unrun in baseline
+//   Type: SVSim.BattleEngine.Rng.HeadlessNetworkBattleMgr
+//   See data_dumps/reports/engine-cleanup/live-methods.baseline.txt
+
 namespace SVSim.BattleEngine.Rng
 {
     // The headless authoritative NETWORK battle mgr — the emitting twin of HeadlessBattleMgr. Emission
@@ -19,6 +23,13 @@ namespace SVSim.BattleEngine.Rng
             _rng = rng ?? new SeededRandomSource(contentsCreator.RandomSeed);
         }
 
+        // Phase-5 chunk 45: overload for the pre-seeded GameMgr path.
+        public HeadlessNetworkBattleMgr(Wizard.BattleMgr.IBattleMgrContentsCreator contentsCreator, IRandomSource rng, GameMgr gameMgr)
+            : base(contentsCreator, gameMgr)
+        {
+            _rng = rng ?? new SeededRandomSource(contentsCreator.RandomSeed);
+        }
+
         public override int StableRandom(int val)
         {
             double unit = _rng.NextUnit();